As a major Saw fanboy - of the first three, at least - I'm going to let it slide that these guys do the noob thing of confusing Jigsaw with Billy the puppet. Because the satire is otherwise spot-on.

Now, if it were me, I'd have added a scene where they evict him, and years later are still finding 50 different pranks he left behind - but only those who stuck through all seven movies would really appreciate that part, perhaps.